1. Field of the Invention
This invention relates to re-writable bubble-domain decoders and more particularly to such decoders utilizing switches which are controlled by both current and a pre-loaded domain. The ability to preload domains into specified switch positions allows re-writability.
2. Description of the Prior Art
Decoders for magnetic bubble domain systems are known in the art as can be seen by referring to U.S. Pat. Nos. 3,689,902; 3,701,125; 3,757,314. These decoders are characterized in that a plurality (2.sup.N) of storage positions, (e.g., shift registers) or logic positions are accessed using a cascade of switches so that only a minimum number (N or 2N) of interconnections and circuits are needed. Preferred directions of bubble domain movement are determined in accordance with the currents applied on a plurality of current carrying control loops which are adjacent to the bubble propagation paths. Consequently, once these current carrying control loops are provided, addressing is achieved in accordance with the current signals produced thereon. These decoders are not re-writable, since the decoder addresses can be changed only by removing and replacing the current-control-loop switches.
U.S. Pat. Nos. 3,753,253 and 3,760,386 describe bubble domain systems in which interactions between magnetic bubble domains are used to provide desired paths of movement of bubble domains. For instance, U.S. Pat. No. 3,753,253 shows the provision of trapped domains at the intersection of propagation paths. The presence of a domain at an intersection causes subsequent domains to take a particular path. If no domain is trapped at the intersection, then subsequent domains will take a second path. Here, the preferred direction of movement through the intersection is determined by the presence and absence of a domain trapped therein. In order to change the direction, the trapped domain must be removed from the intersection or placed there. It is not possible to place a domain permanently at an intersection and yet have the switch at that intersection be able to effect selection between two states to provide a selected output path for subsequent domains.
U.S. Pat. No. 3,760,386 is similar to U.S. Pat. No. 3,753,253 in that the control domain, which is used to provide bubble domain interactions to determine a desired output path, is either present or absent depending upon the output path desired. It is not possible to provide a plurality of output paths if the control domain always remains trapped at the intersection.
The prior art which relies upon placing and removing a control domain at an intersection of propagation paths involves additional hardware and timing circuitry. Generally, it is less efficient to have to constantly insert control domains and remove control domains in order to change the preferred path of subsequent domains through a switch. More timing is involved for this operation, additional delays are introduced, and additional power requirements are present.
Accordingly, it is a primary object of this invention to provide a switch with its position defined by the loading of a control domain, but with its switch action provided by an activating current.
It is an additional important object of this invention to provide a rewritable bubble domain decoder which has a universal structure but is personalizable as well as rewritable.
It is another object of the present invention to provide a rewritable bubble domain circuit which does not require extensive timing circuits or excessive power to achieve the circuit function.
It is a further object of this invention to provide a rewritable circuit whose addresses for bubble domain propagation can be readily changed with a minimum number of interconnections to the magnetic chip in which the bubble domains exist.
It is a still further object of this invention to provide redundancy in a magnetic chip in order to improve the yield of such chips, using a technique which is simple, consumes low power, and requires a minimum of circuitry.
It is also an object of this invention to provide hardware and a method of operation for applications where alterable and re-positionable switches are needed.